Imaging system with improved image quality and associated methods

ABSTRACT

An image capturing device may include a detector including a plurality of sensing pixels, and an optical system adapted to project a distorted image of an object within a field of view onto the sensing pixels, wherein the optical system expands the image in a center of the field of view and compresses the image in a periphery of the field of view, wherein a first number of sensing pixels required to realize a maximal zoom magnification {circumflex over (Z)} at a minimum resolution of the image capturing device is less than a square of the maximal zoom magnification times a second number of sensing pixels required for the minimum resolution.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments are directed to an imaging system, more particularly to animaging system having improved image quality and associated methods.

2. Description of Related Art

Recently, image capturing devices have become widely used in portableand non-portable devices such as cameras, mobile phones, webcams andnotebooks. These image capturing devices conventionally include anelectronic image detector such as a CCD or CMOS sensor, a lens systemfor projecting an object in a field of view (FOV) onto the detector andelectronic circuitry for receiving, processing, and storing electronicdata provided by the detector. Resolution and optical zoom are twoimportant performance parameters of such image capturing devices.

Resolution of an image capturing device is the minimum distance twopoint sources in an object plane can have such that the image capturingdevice is able to distinguish these point sources. Resolution depends onthe fact that, due to diffraction and aberrations, each optical systemprojects a point source not as a point but a disc of predetermined widthand having a certain light intensity distribution. The response of anoptical system to a point light source is known as point spread function(PSF). The overall resolution of an image capturing device mainlydepends on the smaller one of the optical resolution of the opticalprojection system and the resolution of the detector.

Herein, the optical resolution of an optical projection system shall bedefined as the full width at half maximum (FWHM) of its PSF. In otherwords, the peak values of the light intensity distribution of aprojection of two point light sources must be spaced at least by theFWHM of the PSF in order for the image capturing device to be able todistinguish the two point light sources. However, the resolution couldalso be defined as a different value depending on the PSF, e.g. 70% ofthe width at half maximum. This definition of the optical resolutionmight depend on the sensitivity of the detector and the evaluation ofthe signals received from the detector.

The resolution of the detector is defined herein as the pitch, i.e.,distance middle to middle of two adjacent sensor pixels of the detector.

Optical zoom signifies the capability of the image capturing device tocapture a part of the FOV of an original image with better resolutioncompared with a non-zoomed image. Herein, it is assumed that inconventional image capturing devices the overall resolution is usuallylimited by the resolution of the detector, i.e. that the FWHM of the PSFcan be smaller than the distance between two neighboring sensor pixels.

Accordingly, the resolution of the image capturing device may beincreased by selecting a partial field of view and increasing themagnification of the optical projection system for this partial field ofview. For example, ×2 optical zoom refers to a situation where allsensor pixels of the image detector capture half of the image, in eachdimension, compared with that of ×1 zoom.

Digital still cameras (DSCs) typically employ several groups of lenselements that are mechanically shifted relative to one another in orderto create a varying focal length for the whole optical system. In mostcommon multi-use devices having cameras incorporated therein, e.g.,mobile phones, notebook computer, web cameras, etc., the optical systemis a fixed-focus system, i.e. there are no moving parts. Thus, it is notpossible to dynamically change the system's focal length. The mostwidespread zoom solution offered in camera phones is “a digital zoom,” asolution based on cropping the image down to a smaller size andinterpolating the cropped image to the original size, where the missinginformation is completed in various ways. This solution only emulatesthe effect of a longer focal length and, by definition, adds no newinformation to the image.

Thus, use of digital zoom often results in an obvious loss of detail inthe zoomed-in image compared to an optical zoom system. As used herein,“digital zoom” refers to signal interpolation where no additionalinformation is actually provided, whereas “optical zoom” refers tomagnification of the projected partial image, providing more informationand better resolution.

In high-end devices, a mechanical zoom mechanism, similar to the zoommechanisms in DSCs, may be employed. These systems may incorporate asmall motor, typically based on piezoelectric plates, which enablemovement of a lens in the Z direction (along the optical axis) and thuscreate a varying focal length. Such a motor may be around 3 mm indiameter and more than 15 mm in length. Further, predicted cost for massproduction is very high compared with fixed-focus lens modules.Additionally, although a mechanical zoom solution provides good qualityimages, the presence of moving parts results in a much greatervulnerability to physical damage and erosion.

Another technology for achieving optical zoom is a liquid zoom lens.Here, the focal length of a lens changes when a pressure orelectro-static force is applied on the liquid inside the lens. However,liquid zoom lens technology suffers from several known problems. Forexample, changing the lens's focal length in order to achieve zoom alsoaffects the focus, i.e., a system of at least two liquid lenses (one forzoom and one for focus correction) is required. It is therefore hard toimplement control mechanisms that enables continuous zoom. Liquid lensesare also known to suffer from pincushion distortion as well as chromaticaberrations. Further, the whole system is characterized by lowdurability and deteriorating performance over time due to mechanicalfatigue.

SUMMARY OF THE PRESENT INVENTION

Embodiments are therefore directed to a digital camera and associatedmethods that substantially overcome one or more of the problems due tothe limitations and disadvantages of the related art.

It is a feature of an embodiment to provide an imaging system having anoptical zoom using a fixed-focus lens, i.e., without any mechanicalmovement mechanism.

It is another feature of an embodiment of the present invention toprovide an imaging system having variable resolution across the imagesensor, e.g., having reduced resolution at the image borders or a largerpixel-sensor area.

It is yet another feature of an embodiment to provide a imaging systemrealizing optical zoom by having distortion that is later on correcteddigitally.

At least one of the above and other features and advantages of thepresent invention may be realized by providing an image capturingdevice, comprising a detector including a plurality of sensing pixels,and an optical system adapted to project a distorted image of an objectwithin a field of view onto the sensing pixels, wherein the opticalsystem expands the image in a center of the field of view and compressesthe image in a periphery of the field of view, wherein a first number ofsensing pixels required to realize a maximal zoom magnification{circumflex over (Z)} at a minimum resolution of the image capturingdevice is less than a square of the maximal zoom magnification times asecond number of sensing pixels required for the minimum resolution.

The first number of sensing pixels may be less than or equal to thesecond number of sensing pixels times 2 ln({circumflex over (Z)})+1,where {circumflex over (Z)} is the maximal zoom magnification. The firstnumber of sensing pixels may be equal to about 1.75 times the secondnumber of sensing pixels.

The optical system may be adapted such that a point spread function inthe periphery of the field of view has a full width at half maximumsubstantially the size of a sensing pixel. The optical system may beadapted such that an optical magnification at the center of the field ofview is more than twice an optical magnification at the periphery of thefield of view.

The optical system may be adapted to provide the distorted image that isseparable in orthogonal directions. The optical system may be adapted toprovide the distorted image that is radially symmetric. The imagecapturing device may further include a processor adapted to manipulateelectronic information output from the detector. The first number ofsensing pixels may have an equal pitch across the detector.

The optical system includes a plurality of lenses. All of the pluralityof lenses may be plastic. Each of the plurality of lenses may be fixedfocus lenses, i.e., there may be no moving lenses.

At least one of the above and other features may be realized byproviding a method of providing zoom to a fixed focus lens system, themethod including receiving an expanded image in a center of a field ofview, receiving a compressed the image in a periphery of the field ofview, and processing a first number of sensing pixels required torealize a maximal zoom magnification at a minimum resolution, whereinthe first number of sensing pixels is less than a square of the maximalzoom magnification times a second number of sensing pixels required forthe minimum resolution.

The first number of sensing pixels may be less than or equal to thesecond number of sensing pixels times 2 ln({circumflex over (Z)})+1,where {circumflex over (Z)} is the maximal zoom magnification. The firstnumber of sensing pixels may be equal to about 1.75 times the secondnumber of sensing pixels.

At least one of the above and other features may be realized byproviding a method of creating an image capturing device, the methodincluding forming an optical system adapted to project a distorted imageof an object within a field, wherein the optical system expands theimage in a center of the field of view and compresses the image in aperiphery of the field of view, providing a detector proximate to theoptical system, the detector having a first resolution higher than asecond resolution of an image to be output, and processing signalsoutput from the detector to provide the image of the first resolutionover a continuous zoom range.

The continuous zoom range may be from ×1 to ×3. The first resolutioncorresponds to a first number of sensing pixels, the second resolutioncorresponds to a second number of sensing pixels, {circumflex over (Z)}is a maximal zoom magnification and the first number of sensing pixelsin the detector is less than {circumflex over (Z)}² times the secondnumber of sensing pixels.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages will become readily apparentto those of skill in the art by describing in detail example embodimentswith reference to the attached drawings, in which:

FIGS. 1A and 1B illustrate a rectangular pattern and a distortedrectangular pattern having distortion that is separable in X & Ycoordinates, respectively;

FIGS. 2A and 2B illustrate an example of a circularly symmetric patternand a distorted circularly symmetric pattern, respectively;

FIGS. 3A to 3D illustrate an object and corresponding displayed imagesfor different zoom levels in accordance with an embodiment;

FIG. 4A illustrates an example of an optical design in accordance withan embodiment;

FIG. 4B illustrates grid distortions produced using the optical designof FIG. 4A;

FIG. 4C illustrates field curvature of the optical design of FIG. 4A;

FIG. 4D illustrates distortion of the optical design of FIG. 4A;

FIG. 5 illustrates a flowchart of an operation of the image processor ofFIG. 4A in accordance with an embodiment;

FIG. 6 illustrates an exploded view of a digital camera in accordancewith an embodiment;

FIG. 7A illustrates a perspective view of a portable computer with adigital camera integrated therein in accordance with an embodiment; and

FIG. 7B illustrates a front and side view of a mobile telephone with adigital camera integrated therein in accordance with an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

U.S. Provisional Application No. 60/825,726, filed on Sep. 15, 2006, andentitled: “DIGITAL CAMERA WITH IMPROVED IMAGE QUALITY” is herebyincorporated by reference in it entirety.

Embodiments will now be described more fully hereinafter with referenceto the accompanying drawings; however, they may be embodied in differentforms and should not be construed as limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey theembodiments to those skilled in the art. In the figures, the dimensionsof layers and regions are exaggerated for clarity of illustration. Likereference numerals refer to like elements throughout.

In accordance with embodiments, an optical zoom may be realized using afixed-focus lens combined with post processing for distortioncorrection. A number of pixels used in the detector may be increasedbeyond a nominal resolution desired to support zoom capability. First,an initial introduction to the concept of using distortion to realizezoom will be briefly discussed.

Commonly assigned, co-pending PCT Application Serial No. EP2006-002864,which is hereby incorporated by reference, discloses an image capturingdevice including an electronic image detector having a detectingsurface, an optical projection system for projecting an object within afield of view (FOV) onto the detecting surface, and a computing unit formanipulating electronic information obtained from the image detector.The projection system projects and distorts the object such that, whencompared with a standard lens system, the projected image is expanded ina center region of the FOV and is compressed in a border region of theFOV.

As disclosed therein, the projection system may be adapted such that itspoint spread function (PSF) in the border region of the FOV has a FWHMcorresponding essentially to the size of corresponding pixels of theimage detector. In other words, this projection system may exploit thefact that resolution in the center of the (FOV) is better than at wideincident angles, i.e., the periphery of the FOV. This is due to the factthat the lens's point spread function (PSF) is broader in the FOVborders compared to the FOV center.

The resolution difference between the on-axis and peripheral FOV may bebetween about 30% and 50%. This effectively limits the observableresolution in the image borders, as compared to the image center.

Thus, the projection system may include fixed-focus optics having alarger magnification factor in the center of the FOV compared to theborders of the FOV. In other words, an effective focal length (EFL) ofthe lens is a function of incident angle such that the EFL is longer inthe image center and shorter in the image borders. Such a projectionsystem projects a distorted image, in which the central part is expandedand the borders are compressed. Since the magnification factor in theimage borders is smaller, the PSF in the image borders will becomesmaller too, spreading on fewer pixels on the sensor, e.g., one pixelinstead of a square of four pixels. Thus, there is no over-samplingthese regions, and there may be no loss of information when the PSF issmaller than the size of a pixel. In the center of the FOV, however, themagnification factor is large, which may result in better resolution.Two discernable points that would become non-discernable on the sensordue to having a PSF larger than the pixel size may be magnified tobecome discernable on the sensor, since each point may be captured by adifferent pixel.

The computing unit may be adapted to crop and compute a zoomed,undistorted partial image from the center region of the projected image,taking advantage of the fact that the projected image acquired by thedetector has a higher resolution at its center than at its borderregion. For normal pictures of the entire field of view, the centerregion is compressed computationally. However, if a zoomed partial imageof a part of the image close to the center is to be taken, this can bedone by simply cropping the partial image and compressing it less or notcompressing it at all, depending on the desired zoom and the degree ofdistortion of the partial image. In other words, with respect to anon-zoomed image, the image is expanded and cropped so that a greaternumber of pixels may be used to describe the zoomed image.

Thus, this zoom matches the definition of optical zoom noted above.However, this optical zoom may be practically limited to about ×2 or ×3.

In order to realize larger zoom magnifications, embodiments are directedto exploiting the tradeoff between the number of pixels used and thezoom magnification. In other words, larger zoom magnifications mayrequire increasing the number of pixels in the sensor to avoidinformation loss at the borders. A number of pixels required to supportcontinuous zoom may be determined from discrete magnifications, where Z₁is the largest magnification factor and Z_(P) is the smallestmagnification factor. The number of pixels required to support thesediscrete zoom modes, considering N pixels to cover the whole FOV may begiven by Equation 1:

$\begin{matrix}{\overset{\sim}{N} = {N + {N\left( {1 - \left( \frac{Z_{2}}{Z_{1}} \right)^{2}} \right)} + {N\left( {1 - \left( \frac{Z_{3}}{Z_{2}} \right)^{2}} \right)} + \ldots + {N\left( {1 - \left( \frac{Z_{P}}{Z_{P - 1}} \right)^{2}} \right)}}} & (1)\end{matrix}$

Rearranging Equation 1, Equation 2 may be obtained as follows:

$\begin{matrix}{\frac{\overset{\sim}{N}}{N} = {P - {\sum\limits_{i = 1}^{P - 1}\left( \frac{Z_{i + 1}}{Z_{i}} \right)^{2}}}} & (2)\end{matrix}$

Substituting Z_(i)−dZ for Z_(i+1) in order to obtain a continuousfunction of Z results in Equation 3:

$\begin{matrix}{\frac{\overset{\sim}{N}}{N} = {P - {\sum\limits_{i = 1}^{P - 1}1} - \frac{2{Z}}{Z_{i}} + \left( \frac{Z}{Z_{i}} \right)^{2}}} & (3)\end{matrix}$

Discarding higher power terms, e.g., above the first term, and replacingsummation with integration, Equation (4) may be obtained:

$\begin{matrix}{\frac{\overset{\sim}{N}}{N} = {{P - \left( {\left( {P - 1} \right) - {2{\int_{i = 1}^{\hat{Z}}\frac{2\ {Z}}{Z_{i}}}}} \right)} = {{2{\ln \left( \hat{Z} \right)}} + 1}}} & (4)\end{matrix}$

where {circumflex over (Z)} is the maximal zoom magnification desired.

In other words, for a standard digital camera, i.e., distortion free,with a rectangular sensor of K Mega Pixels ([MP]) producing an image ofL [MP] (L<K), the maximum applicable optical zoom (for L[MP] image) forthe entire image may be limited to

$\sqrt{\frac{K}{L}}.$

In other words, for a desired optical zoom, Z, K equals Z² times L.

Thus, when the zoom required is ×2, a standard camera requires fourtimes more pixels. However, in accordance with embodiments, higher zoommay be realized at the center of the image due to the distortingmechanism the optics introduces. Thus, as can be seen from Equation 4above, only approximately 2.38 times as many pixels may be needed for an×2 zoom. For example, using a standard 2 MP image sensor, applying 2×zoom will require 4.77 MP for a completely lossless zoom. Relaxingdemands on the quality in image borders, i.e., allowing loss ofinformation, will decrease this number, e.g., down to about 1.75 timesas many pixels for ×2 zoom.

FIGS. 1A and 1B illustrate an original rectangular pattern and aprojected rectangular pattern as distorted in accordance with anembodiment, respectively. In this specific example, the transformationrepresenting the distortion is separable in the horizontal and verticalaxes. FIGS. 2A and 2B illustrate an original circularly symmetricpattern and a projected circularly symmetric pattern as distorted inaccordance with an embodiment, respectively. As can be seen therein, thepatterns are expanded in a central region and compressed in a borderregion. Other types of distortion, e.g., anamorphic distortion, may alsobe used.

FIGS. 3A to 3D illustrate a general process of imaging an object, shownin FIG. 3A, in accordance with embodiments. The object is firstprojected and distorted by a lens system in accordance with anembodiment and captured by a high resolution, i.e., K[MP] detector, inFIG. 3B. A corrected lower resolution, i.e., L[MP] image with a ×1 zoomis illustrated in FIG. 3C. A corrected ×2 zoom image, having the sameL[MP] resolution as the ×1 image, is shown in FIG. 3D.

FIG. 4A illustrates an example imaging capturing device 400 including anoptical system 410 for imaging an object (not shown) onto a detector475, i.e., an image plane, that outputs electrical signals in responseto the light projected thereon. These electrical signals may be suppliedto a processor 485, which may process, store, and/or display the image.The optical system 410 may include a first lens 420 having second andthird surfaces, a second lens 430 having fourth and fifth surfaces, anaperture stop 440 at a sixth surface, a third lens 450 having seventhand eight surfaces, a fourth lens 460 having ninth and tenth surfaces,an infrared (IR) filter 470 having eleventh and twelfth surfaces, all ofwhich image the object onto the image plane 475.

In this particular example, the optical system 410 may have a focallength of 6 mm and an F-number of 3.4. The optical system 410 accordingto an embodiment may provide radial distortion having image expansion inthe center and image compression at the borders for a standard FOV of±30°.

The optical design coefficients and the apertures of all opticalsurfaces along with the materials from which the lenses may be made areprovided as follows:

TABLE 1 Radius Thick Semi- Parameter Parameter Parameter ParameterParameter # Note (mm) (mm) Medium Diameter Conic X2 X4 X6 X8 X10 0 OBJInfinite Infinite Air 653.2 0.000 0.000 0.000 0.000 0.000 0.000 1Infinite 0.30 Air 4.0 −0.932 0.000 0.000 0.000 0.000 0.000 2 L1 2.9001.68 Plastic 3.0 −100.00 0.000 0.017 −0.001 0.000 0.000 3 1000 0.17Plastic 2.5 −100.00 0.000 0.022 −0.001 0.000 0.000 4 L2 112.00 1.47Plastic 2.4 0.455 0.000 −0.027 −0.001 0.000 0.000 5 2.700 1.68 Plastic1.6 0.000 0.000 0.000 0.000 0.000 0.000 6 APS Infinite 0.05 Air 0.412.800 0.000 −0.067 −0.049 0.000 0.000 7 L3 3.266 0.80 Plastic 0.6 8.0000.000 0.066 0.044 0.000 0.000 8 −3.045 0.63 Plastic 0.9 2.979 0.0000.000 0.075 0.000 0.000 9 L4 −2.504 1.51 Plastic 1.1 22.188 0.000 −0.3120.175 −0.055 0.010 10 −7.552 0.39 Plastic 1.6 0.000 0.000 0.000 0.0000.000 0.000 11 IRF Infinite 0.30 N-BK7 1.8 0.000 0.000 0.000 0.000 0.0000.000 12 Infinite 0.23 Air 1.9 0.000 0.000 0.000 0.000 0.000 0.000 13IMG Infinite 0.00 1.8 0.000 0.000 0.000 0.000 0.000 0.000

Here, surface 0 corresponds to the object, L1 corresponds to the firstlens 420, L2 corresponds to the second lens 430, APS corresponds to theaperture stop 440, L3 corresponds to the third lens 450, L4 correspondsto the fourth lens 460, IRF corresponds to the IR filter 460 and IMGcorresponds to the detector 475. Of course, other configurationsrealizing sufficient distortion may be used.

Plastic used to create the lenses may be any appropriate plastic, e.g.,polycarbonates, such as E48R produced by Zeon Chemical Company, acrylic,PMMA, etc. While all of the lens materials in Table 1 are indicated asplastic, other suitable materials, e.g., glasses, may be used.Additionally, each lens may be made of different materials in accordancewith a desired performance thereof. The lenses may be made in accordancewith any appropriate method for the selected material, e.g., injectionmolding, glass molding, replication, wafer level manufacturing, etc.Further, the IR filter 470 may be made of suitable IR filteringmaterials other than N-BK7.

FIG. 4B illustrates a grid distortion provided by the optical system410. FIG. 4C illustrates field curvature of the optical system 410. FIG.4D illustrates distortion of the optical system 410.

FIG. 5 illustrates a flowchart of an operation that may be performed bythe processor 485. The processor 485 may include an image signalprocessing (ISP) chain 510 that receives an image from the detector 475.This image may be, for example, raw Bayer data or a bitmap image. Theimage may be supplied to operation 530 via an input interface 520.Operation 530 may also receive contributing pixel indices from operation525, which determines, for every pixel index in an undistorted outputimage, close neighbors from the distorted input image. Then, knowing thedistortion function of the lens system 410, and since the distortion isfixed, each pixel in the distorted image has a known and fixedmagnification factor, thus operation 530 may correct the distortion.Correcting the distortion may be done using known transformations thatcalculate, according to the preconfigured desired zoom magnification,for every pixel in the desired undistorted image, which pixels from thedistorted image contribute to it (as there might not be a pixel-to-pixelmatching between the distorted and undistorted image, interpolationbetween several neighboring distorted pixels may be used to determinethe value of the corresponding undistorted pixel). Thus, both 1×magnification, in which the center of the image simply becomes morecompressed, and higher magnification factors, where a desired section iscropped from the image center and corrected without compression (or withless compression, according to the desired magnification), may both berealized.

For example, when zoom is set to ×1, operation 530 may be adapted tocompute an undistorted picture, with fixed L[MP] resolution, of theprojected object data received from the detector 475. The detector 475may generate data corresponding to the distorted projection of theobject to be captured. For this purpose, the distortion generated by theprojection system may be known, estimated or measured. When the zoom ishigher, operation 530 may adapt the image and crop the desired center ofthe image, thus receiving the desired zoom with same L[MP] resolution.

Operation 530 may use any suitable interpolation method, e.g., bilinear,spline, edge-sense, bicubic spline, etc., and may output the resultantpixel values to an output interface 540. If needed in accordance with adesired end use, image contrast of the output image may be improved inoperation 550. Then, the output image may be returned to the ISP chain510, where further processing may be performed on the image, e.g.,denoising or compression, such as JPEG compression or GIF compression.

The dashed connector between the input interface 520 and operation 525may be provided if the image capturing device is to operate in more thanone image capture mode, e.g., a normal mode and a zoom mode. If so,different distortion corrections may be needed for each mode, so theinput interface 520 might provide the image capture mode information tooperation 525.

FIG. 6 illustrates an exploded view of a digital camera 600 in which anoptical zoom system in accordance with embodiments may be employed. Asseen therein, the digital camera 600 may include a lens system 610 to besecured to a lens holder 620, which, in turn, may be secured to a sensor630. Finally, the entire assembly may be secured to electronics 640.

FIG. 7A illustrates a perspective view of a computer 680 having thedigital camera 600 integrated therein. FIG. 7B illustrates a front andside view of a mobile telephone 690 having the digital camera 600integrated therein. Of course, the digital camera 600 may be integratedat other locations than those shown.

Thus, in accordance with embodiments, an optical zoom may be realizedusing a fixed-focus lens combined with post processing for distortioncorrection. A number of pixels used in the detector may be increasedbeyond a nominal resolution desired to support zoom capability.

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Further, although terms suchas “first,” “second,” “third,” etc., may be used herein to describevarious elements, components, regions, layers and/or sections, theseelements, components, regions, layers and/or sections should not belimited by these terms. These terms are only used to distinguish oneelement, component, region, layer and/or section from another. Thus, afirst element, component, region, layer and/or section could be termed asecond element, component, region, layer and/or section withoutdeparting from the teachings of the embodiments described herein.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” etc., may be used herein for ease of description to describethe relationship of one element or feature to another element(s) orfeature(s), as illustrated in the figures. It will be understood thatthe spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

As used herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and “including” specify the presence of statedfeatures, integers, steps, operations, elements, components, etc., butdo not preclude the presence or addition thereto of one or more otherfeatures, integers, steps, operations, elements, components, groups,etc.

Embodiments of the present invention have been disclosed herein and,although specific terms are employed, they are used and are to beinterpreted in a generic and descriptive sense only and not for purposeof limitation. While embodiments of the present invention have beendescribed relative to a hardware implementation, the processing ofpresent invention may be implemented in software, e.g., by an article ofmanufacture having a machine-accessible medium including data that, whenaccessed by a machine, cause the machine to undistort the data. Further,while the above discussion has assumed the pixels have an equal pitchacross the detector, some of all of the compression may be realized byaltering the pitch across the detector. Accordingly, it will beunderstood by those of ordinary skill in the art that various changes inform and details may be made without departing from the spirit and scopeof the present invention as set forth in the following claims.

1. An image capturing device, comprising: a detector including aplurality of sensing pixels; and an optical system adapted to project adistorted image of an object within a field of view onto the sensingpixels, wherein the optical system expands the image in a center of thefield of view and compresses the image in a periphery of the field ofview, wherein a first number of sensing pixels required to realize amaximal zoom magnification {circumflex over (Z)} at a minimum resolutionof the image capturing device is less than a square of the maximal zoommagnification times a second number of sensing pixels required for theminimum resolution.
 2. The image capturing device as claimed in claim 1,wherein the first number of sensing pixels less than or equal to thesecond number of sensing pixels times 2 ln({circumflex over (Z)})+1,where {circumflex over (Z)} is the maximal zoom magnification.
 3. Theimage capturing device as claimed in claim 1, wherein the first numberof sensing pixels is equal to about 1.75 times the second number ofsensing pixels.
 4. The image capturing device as claimed in claim 1,wherein the optical system is adapted such that a point spread functionin the periphery of the field of view has a full width at half maximumsubstantially the size of a sensing pixel.
 5. The image capturing deviceas claimed in claim 1, wherein the optical system is adapted such thatan optical magnification at the center of the field of view is more thantwice an optical magnification at the periphery of the field of view. 6.The image capturing device as claimed in claim 1, wherein the opticalsystem is adapted to provide the distorted image that is separable inorthogonal directions.
 7. The image capturing device as claimed in claim1, wherein the optical system is adapted to provide the distorted imagethat is radially symmetric.
 8. The image capturing device as claimed inclaim 1, further comprising a processor adapted to manipulate electronicinformation output from the detector.
 9. The image capturing device asclaimed in claim 1, wherein the first number of sensing pixels haveequal pitch across the detector.
 10. The image capturing device asclaimed in claim 1, wherein the optical system includes a plurality oflenses.
 11. The image capturing device as claimed in claim 10, whereineach of the plurality of lenses are plastic.
 12. The image capturingdevice as claimed in claim 10, wherein each of the plurality of lensesare fixed focus lenses.
 13. A mobile phone including an image capturingdevice according to claim
 1. 14. A portable computer including an imagecapturing device according to claim
 1. 15. A method of providing zoom toa fixed focus lens system, the method comprising: receiving an expandedimage in a center of a field of view; receiving a compressed the imagein a periphery of the field of view; and processing a first number ofsensing pixels required to realize a maximal zoom magnification at aminimum resolution, wherein the first number of sensing pixels is lessthan a square of the maximal zoom magnification times a second number ofsensing pixels required for the minimum resolution.
 16. The method asclaimed in claim 15, wherein the first number of sensing pixels lessthan or equal to the second number of sensing pixels times 2ln({circumflex over (Z)})+1, where {circumflex over (Z)} is the maximalzoom magnification.
 17. The method as claimed in claim 15, wherein thefirst number of sensing pixels is equal to about 1.75 times the secondnumber of sensing pixels.
 18. A method of creating an image capturingdevice, the method comprising: forming an optical system adapted toproject a distorted image of an object within a field, wherein theoptical system expands the image in a center of the field of view andcompresses the image in a periphery of the field of view; providing adetector proximate to the optical system, the detector having a firstresolution higher than a second resolution of an image to be output; andprocessing signals output from the detector to provide the image of thefirst resolution over a continuous zoom range.
 19. The method as claimedin claim 18, wherein the continuous zoom range is from ×1 to ×3.
 20. Themethod as claimed in claim 18, the first resolution corresponds to afirst number of sensing pixels, the second resolution corresponds to asecond number of sensing pixels, {circumflex over (Z)} is a maximal zoommagnification and the first number of sensing pixels in the detector isless than {circumflex over (Z)}² times the second number of sensingpixels.